Boron monofluoride

Boron monofluoride
Other names

Boron fluoride

Boron(I) fluoride
Fluoroboronene

Fluoroborylene
Identifiers
CAS number 13768-60-0
PubChem 6336604
ChemSpider 4891729 Y
EC number 237-383-0
Jmol-3D images Image 1
Properties
Molecular formula BF
Molar mass 29.81 g mol−1
Exact mass 30.007708671 g mol-1
Thermochemistry
Std enthalpy of
formation ΔfHo298		 115.90 kJ mol-1
Standard molar
entropy So298		 200.48 J K-1 mol-1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

boron monofluoride or fluoroborylene is a chemical compound with formula BF, one atom of boron and one of fluorine. It was discovered as an unstable gas and only in 2009 found to be a stable ligand combining with transition metals, in the same way as carbon monoxide. It is a subhalide, containing fewer than the normal number of fluorine atoms, compared with boron trifluoride. BF is isoelectronic with carbon monoxide and dinitrogen.

Contents

Structure

The experimental B-F bond length is 1.263 angstrom [1]. One reported computed bond order for the molecule is 1.4. [2]

Preparation

Boron monofluoride can be prepared by passing boron trifluoride gas at 2000 °C over a boron rod. It can be condensed at liquid nitrogen temperatures (-196°).[3]

Reactions

BF can react with itself to form polymers of boron containing fluorine with between 10 and 14 boron atoms. BF reacts with BF3 to form B2F4. BF and B2F4 further combine to form B3F5. B3F5 is unstable above -50° and forms B8F12. This substance is a yellow oil.[3]

BF reacts with acetylenes to make the 1,4-diboracyclohexadiene ring system. BF can condense with 2-butyne forming 1,4-difluoro-2,3,5,6-tetramethyl-1,4-diboracyclohexadiene. Also it reacts with acetylene to make 1,4-difluoro-1,4-diboracyclohexadiene.[3]

Ligand

The first case of BF being a ligand on a transition element was demonstrated in 2009 with the compound (C5H5)2Ru2(CO)4(μ-BF). The BF was bound to both ruthenium atoms as a bridge.[4] Vidovic and Aldridge reacted NaRu(CO)2(C5H5) with (Et2O):BF3.[5] Note that the BF was formed in place rather than added on.

Earlier in 1968 K. Kämpfer, H. Nöth, W. Petz, and G. Schmid claimed that Fe(BF)(CO)4 was formed in the reaction of B2F4 with Fe(CO)5, however this has not been reproduced.[5]

References

  1. ^ G. Cazzoli, L. Cludi, C. Degli Esposti, L. Dore, The millimeter and submillimeter-wave spectrum of boron monofluoride: Equilibrium structure, Journal of Molecular Spectroscopy, Volume 134, Issue 1, March 1989, Pages 159-167, ISSN 0022-2852, doi:10.1016/0022-2852(89)90138-0
  2. ^ Bond Order and Chemical Properties of BF, CO, and N2 Ryan J. Martinie, Jarred J. Bultema, Mark N. Vander Wal, Brandon J. Burkhart, Douglas A. Vander Griend, Roger L. DeKock Journal of Chemical Education 2011 88 (8), 1094-1097 doi:10.1021/ed100758t
  3. ^ a b c P. L. Timms (1972). Low Temperature Condensation. p. 143. ISBN 0120236141. http://books.google.com.au/books?id=VupzlLU9NB0C&pg=PA143&lpg=PA143#v=onepage&q&f=false. 
  4. ^ Liancai Xu, Qian-shu Li, Yaoming Xie, R. Bruce King and Henry F. Schaefer (30 December 2009). "Prospects for Making Organometallic Compounds with BF Ligands: Fluoroborylene Iron Carbonyls". Inorganic Chememistry, 2010 49 (3): 1046–1055. doi:10.1021/ic901964f. 
  5. ^ a b Liancai Xu et al (2010). "Binuclear fluoroborylene manganese carbonyls". Inorganica Chimica Acta.